We plan to continue designing and synthesizing fluorescent dyes to be used as optical probes for measuring potential differences across biological membranes. We also will study the spectroscopic and membrane binding properties of dyes that have been shown to change their fluorescence when incorporated into nerves and the nerves are stimulated. By doing this we hope to better understand the mechanisms for the fluorescence changes observed in nerve. We will be able to synthesize new dyes that are more sensitive to changes in membrane potential.